Turning bars for use in a system for manufacturing and processing web material are known. Typically, these known turning bars are found in a web manufacturing machine to turn or redirect a moving web from one direction to another; i.e., to direct the moving web to a finishing station away from the machine direction and then redirect the finished web toward the machine.
The typical turning bar is a unitary component fixed relative to the web manufacturing machine. Since it is fixed and does not rotate, at least one drawback to the known turning bar is that dust accumulates on the turning bar, particularly in the manufacture of a paper web material such as tissue paper. Dust accumulation and subsequent dust clumping on the turning bar have the potential to adversely affect the quality of a finished product, as well as system or machine runnability if the dust accumulates and subsequently falls into the product, for instance, during packaging.
Dust clumping occurs, for example, when the standard fixed turning bar generates static electricity. The non-rotating turning bar thus attracts and holds dust during operation of the system. When the system is even momentarily stopped, dust clumps, which have been held to the turning bar by static electricity, fall into the product, which leads to degraded product quality and consumer dissatisfaction.
Attempts to address the dust accumulation problem include use of compressed air to blow dust off the web before it accumulates on the turning bar or elsewhere. By way of example, a Coanda nozzle is described in U.S. Pat. No. 5,577,294 to Pollock for a xe2x80x9cWeb Cleaner Apparatus and Method.xe2x80x9d In Pollock, the Coanda nozzle directs a gas flowing at a high rate of speed in a direction generally opposed to the moving web of sheet material for cleaning a substantially planar surface of the moving web material.
In addition to Pollock, a variety of other air nozzle configurations and area dust containment and removal systems have been tried over the years to address the problems of dust accumulation and clumping. In general, however, compressed air and similar methods tend to create environmental dust problems in a web machine""s operating area, which may require workers to don protective masks for respiratory protection and may necessitate costly air-scrubbers to control the blown dust. Accordingly, many previous dust accumulation prevention techniques and apparatuses have tended to increase manufacturing and consumer costs with debatable success.
The present invention is directed to a turning bar assembly rotatably disposed adjacent a web of material moving at an operational speed in a web forming device. The component parts of the invention are simple, reliable, and economical to manufacture, assemble, and use. Other advantages of the invention will be apparent from the following description and the attached drawings or can be learned through practice of the invention.
According to an aspect of the invention, a turning bar assembly is rotatably disposed adjacent a web of material moving at an operational speed of approximately 12-13% of the web speed in a web forming device. The relative speed of 12-13% is provided by way of example only, since the turning bar assembly can be controllably rotated relative to the web at any speed at least less than the speed of the web.
The turning bar assembly includes a roller or a turning bar, which receives, turns and transfers the web down or across stream in the web forming device. For instance, the turning bar may be oriented at 45xc2x0 to the moving web and when the web contacts the turning bar, the direction of the web is changed 90xc2x0. Such redirection or sheet turning by the turning bar may be desirable, for instance, if the web is to be finished at a finishing station located away from the longitudinal direction of the web forming device. Upon finishing the web, another turning bar assembly may be provided downstream to further redirect the web.
The turning bar in one aspect of the invention has a first and a second end. A first mounting end or first mount is attached to the first end and a second mounting end or second mount is attached to the second end. The first end is disposed apart from the second end at a distance of between ten to about forty inches, and an outer diameter of the turning bar is between one inch to about three inches to accommodate the standard web material dimensions. It is within the scope of the invention that the length and the outer diameter of the turning bar can be increased or decreased. Also in this aspect, the turning bar is configured to be controllably rotated 360 degrees relative to the first and second mounts at a speed less than the operational speed of the moving web, such as 1-50% of the web speed, or more specifically 10-20% of the web speed. Web speed can be calculated in a variety of ways and be within the scope of the invention.
According to another aspect of the inventive turning bar assembly, a central or center shaft is disposed longitudinally within the turning bar and fixed to the first and second mounts. In this arrangement, the turning bar is rotatably disposed about the shaft. The turning bar and shaft combination is configured to be removable from the assembly for maintenance and replacement.
In further detail, the turning bar assembly in this aspect includes a plurality of bearings rotatably disposed within the turning bar and about the shaft. The turning bar and the plurality of bearings cooperate to rotate at substantially the operational speed of the moving web. Although the shaft described herein is a unitary shaft extending substantially the length of the turning bar, it is contemplated that the shaft could be formed in multiple pieces. For instance, those portions of the shaft attached to the first and second ends could be severed and apart from each other such that the separate shaft portions extend into the turning bar a sufficient length to support a bearing assembly and be within the scope of the invention.
This aspect also includes a drive apparatus operably connected with the turning bar to rotate the turning bar between about {fraction (1/100)} to about ⅕ of the operational speed of the moving web. The drive apparatus may include in one embodiment a rod or drive shaft, a drive belt, and a motor or other control mechanism. The drive belt is disposed about a portion of the turning bar and a portion of the rod. The drive belt rotates the turning bar when the rod is rotated by the motor. It is to be noted that a single drive shaft could extend the length of the web-forming device with a plurality of drive belts depending from the single drive shaft and operably connected to a plurality of turning bars. Alternatively, it is contemplated that each of the plurality of turning bars could be controllably rotated by individual drive shafts and drive belts or other independent drive mechanisms and remain within the invention""s scope.
In another aspect of the invention, a web forming system is provided, which has a turning bar assembly disposed adjacent a moving web similar to the foregoing embodiment. In this aspect, at least one bearing assembly is disposed concentrically about the shaft within the turning bar. The bearing assembly is configured to allow the turning bar to rotate about the shaft and includes a plurality of bushings and bearings to rotatably attach the turning bar about the shaft. The bushings may be bronze bushings, phenolic bushings, or of other suitable materials to adapt the first and second ends to the shaft.
Once mounted in the web-forming device, the bushings and bearings permit the turning bar to continuously change an aspect or a portion contacting the moving web. Due to this controlled rotation, the dust is substantially constantly dispersed by the turning bar rotating at a speed less than the moving web, which creates drag to prevent dust accumulation and build-up on any single point of the turning bar and the web. Drag also controls sheet handling since the web will xe2x80x9cwalk outxe2x80x9d of the machine if the turning bar is permitted to free-wheelingly rotate. If desired, the turning bar can be configured to rotate in a direction opposite the moving web to further prevent dust accumulation on the turning.
In a further aspect of the invention, a turning bar assembly for use in manufacturing a paper web is provided. The turning bar as generally described above is affixed to a holder and configured to redirect the web from moving in one direction to moving in another direction as the web passes across the turning bar. More specifically, in this embodiment, a tube-like sleeve is rotatably disposed about the turning bar and rotates about the turning bar at substantially less than the operational speed of the web. Stated alternatively, the turning bar is fixed in this aspect while the tubular sleeve, for instance, rotates around the fixed turning bar and a plurality of bearings is disposed about the turning bar. The plurality of bearings in this aspect could be substituted with, for instance, plastic or bronze bushings, lubricant such as grease and the like and still permit the sleeve to rotate about the fixed turning bar.
According to another aspect of the invention, a method for precluding dust accumulation on a turning bar in a web manufacturing system is disclosed, which includes the steps of providing a turning bar rotatably disposed against a moving web of material; redirecting the moving web by the turning bar from a first incoming direction to a second outgoing direction; dispersing a dust originating from the moving web away from the turning bar by rotating the turning bar; and controlling the rotation of the turning bar between about 1% a speed of the moving web to some rotation speed less than the speed of the web.